I removed the Universal 5411 on my previous boat that way. Definitely attach the main halyard to the boom and not rely on the topping lift. Make sure the block and tackle you use can lower the engine all the way to ground. We were about a foot short which meant some scrambling and rethinking at the end to get it on the ground. I think the entire operation of disconnecting the engine and pulling it out took two of us about 2 hours.